1. Field of the Invention
The invention relates to apparatus for the manufacture of zig zag wire ring binders in which a continuous wire has oppositely extending legs connected by relatively wide bends at one end and relatively narrow bends at the other, the wire passing through holes in the sheets being bound. The invention is particularly concerned with the formation of this binder at a point after its preliminary zig zag shape has been formed.
2. Description of the Prior Art
Brook et al. U.S. Pat. No. 3,064,694 shows a wire forming machine in which a pair of companion rolls receive a wire having a preliminary zig zag formation. These rolls have grooves decreasing in width and pitch toward the ends of the rolls to squeeze the bends of the zig zag wire into closer formation. A drawback of this previous construction is the fact that considerable friction is created between the wire bends and the narrowing grooves, as these grooves attempt to continuously deform the wire bends received therein. It has been found that this high friction not only detracts from the efficiency of operation of the device, but tends in some cases to bend the opposite ends of the wire down past the bottom support plate disposed between the companion die rolls, thus creating unwanted deformation of the wire.